If you are thinking of trying this or just want to know how it will feel. Take the side cover of the bike and go for a short ride. the bike will not idle with the cover of but under throttle you can tell the differance. Short ride! you will be running lean!
If you want to do the mod you will have to rejet your carb.
you will need a 140 or higher main jet "I went with a 142"
and a 25 pilot jet
First remove the seat then the tank.
To make it easy to remove thr carb take the top bolt out of the rear frame and roll the frame back.
Then remove the throttle cable's from the carb, remove TPS or find the plug and unplug it, and lossen the boots to pull the carb.
Once the carb is off you will have to take a 1/8 drill and drill out the cover on the fuel screw. Drill a small hole then scew a screw into the hole and use a set of plyers to pull the cover plug out.
Then you can see the fuel screw. Take a flat head and run the screw all the way in. Then turn the screw back out 2 1/2 to 3 turns back out to match the jets.
Now tack the bottom off the carb and replace the main and pilot jets. I forgot to take pics but there is a video on the whole thing that will show you step by step.Suzuki DRZ400 3X3 mod
I used a jigsaw but you can cut the air box with almost anything.
Last step put it all back together and get ready to grin!
I love it! If you have a DRZ and want to feel the change we can get together and you can ride mine.